Device for the separation of elements of a gas mixture by adsorption

ABSTRACT

A device for separating at least one component from a gas mixture, comprising at least a pair of adsorber units, each adsorber unit comprising an envelope defining an inner volume having a lower end zone and an upper end zone. There is at least one adsorbent layer between the lower and upper end zones. A first conduit has one end communicating with the lower end zone, and a second conduit has one end communicating with the upper end zone. The adsorber units of the pairs are superposed and one of the first and second conduits of each adsorber includes a vertical central tube portion. The vertical central tube portions of the pair of adsorber units are mechanically interconnected in endwise abutting relationship. The adsorber units are superposed such that the envelopes of adjacent units leave an intermediate space therebetween. The first and second conduits each have an outer portion extending out of the envelope in the intermediate space.

The present invention relates to devices for the separation of elementsof a gas mixture, of the type comprising at least two adsorbers eachdefining an internal volume having a lower end zone and an upper endzone and means for bringing the upper and lower end zones of theadsorbers into selective communication with fluid circuits.

Separation devices of this type are essentially used, in pressure ortemperature variation technologies called PSA or TSA, for theproduction, starting with a gas mixture, of a gaseous constituent ofthis mixture, especially of a constituent of air, oxygen or nitrogen, orfor the purification of a gas mixture, especially of feed air for acryogenic air separation unit, also for the production of a constituentof air, oxygen and/or nitrogen and/or argon, and generally employ atleast one of the adsorbents chosen from the group comprising zeolites,activated carbon, alumina or silica gels. Examples of these technologiesare described especially in the documents U.S. Pat. No. 5,223,004,EP-092,153, U.S. Pat. No. 3,338,030 or U.S. Pat. No. 5,137,548. In theknown devices, generally comprising two to four adsorbers, the latterare arranged vertically one beside the other, in a battery, with muchpipework provided with valving, connecting the lower and upper parts ofthe various adsorbers to the fluid circuits. In addition, inapplications employing the alternation of hot and cold gases, theadsorbers, which in practice are not thermally insulated, have to bearranged at a certain horizontal distance away from each other.

The object of the present invention is to propose a device forseparation by adsorption having a particularly compact and closely-builtconfiguration and being suitable for various applications.

In order to do this, according to one characteristic of the invention,the adsorbers are superposed.

According to other characteristics of the invention:

--the means for bringing into communication with the fluid circuitscomprise, for each adsorber, a vertical central tube having one endcommunicating with a lower or upper end zone of the internal volume andthe other end of which is connected to one of the said fluid circuits;

--the central tubes are mechanically connected to each other and to thevertically opposed end walls of the device.

The present invention also relates to the applications of such devicesfor the production, by separation, of a constituent of a gas mixture,especially of hydrogen from a gas mixture containing hydrogen, of oxygenor of nitrogen from air, or, for the purification in terms of oxides ofcarbon and in terms of water, of air delivered to a cryogenic airseparation unit.

Other characteristics and advantages of the present invention willemerge from the following description of embodiments given by way ofillustration but in no way limiting, given in relation with the appendeddrawings in which:

FIG. 1 is a diagrammatic view in vertical section of a first embodimentof a device according to the invention;

FIG. 2 is a diagrammatic view in vertical section of a second embodimentof the invention; and

FIG. 3 is a diagrammatic view in vertical section of a third embodimentof a device according to the invention.

In the description which will follow, and in the drawings, identical orsimilar elements bear the same reference numbers, possibly with.indices.

In the embodiment of FIG. 1, the device includes three identicalsuperposed adsorbers 1A, 1B, 1C, each consisting of a peripheralcylindrical wall 2A, 2B, 2C and of transverse end walls in the form ofupper 3A, 3B, 3C and lower 4₁, 4A, 4B, 4C cupolas. The upper cupola 3A,3B, 3C typically includes an opening 5A, 5B, 5C for filling with theadsorber in order to form therein at least one bed of adsorbent. Theadsorbers are connected to each other by cylindrical skirts 6C and 6Bsurrounding a space between the adjacent adsorbers, the assembly beingsupported on a lower skirt 6A integral with the lower adsorber 1A. Inthe embodiment shown, each adsorber includes a vertical coaxial centraltube 7A, 7B, 7C emerging into the upper zone of the internal volume ofeach adsorber and passing through the lower bottom 4A, 4B, 4C of theadsorber in order to be prolonged in a horizontal section of piping 8A,8B, 8C extending into the space beneath each adsorber for the connectionto a fluid circuit. Each adsorber also includes a tube 9A, 9B, 9Cpassing through the lower wall and emerging into the lower zone of eachadsorber, also for connection to a fluid circuit.

As my be easily seen in FIG. 1, the superposed arrangement of theadsorbers and the concentric construction of the tubes 7A, 7B, 7Cenables the floor-space requirement of the device to be considerablyreduced and greatly facilitates its installation on production orutilization sites. In addition, in this vertical arrangement, it is thesmall surfaces (rounded ends) of the adsorbers which are neighboring,thereby enabling thermal interference between two adjacent adsorbers tobe reduced. Furthermore, this interference may easily be virtuallyeliminated by arranging, in the connecting skirts 6B and 6C, at leastone thermally insulating material, as shown at 10 in the figure.

A greater compactness and an even more effective reduction in thethermal interference, even without insulation, between two adsorbers isobtained with the embodiment shown in FIG. 2. In this embodiment havingtwo adsorbers 1A and 1B, the two central tubes 7A and 7B aremechanically coupled to each other in the space defined in the skirt 6Bbetween the facing domed bottoms 3A and 4B and emerge respectively intothe lower zone of the lower adsorber 1A and into the upper zone of theupper adsorber 1B. Each tube 7A, 7B communicates, via a valve, with anozzle pipe 11A, 11B for connection to the fluid circuits and to eachother via a by-pass nozzle pipe 12 equipped with a valve. In asymmetrical manner, the nozzle pipe 9B, which communicates with thelower zone of the upper adsorber, and the nozzle pipe 9A, which herepasses through the upper wall 3A of the lower adsorber 1A in order tocommunicate with the upper zone of the latter, communicate, via valves,with a common nozzle pipe 13 for connection to the fluid circuit.

The embodiment of FIG. 3, making use of the symmetrical arrangement ofthe adsorber beds rendering pointless the construction of a thermalinsulation between the two adsorbers, uses a single central tube 7, theends of which are connected to the opposed end walls 3B and 4A of theupper 1B and lower 1A beds, the upper bed 1B being without a lower wall(4B), corresponding to the lower wall 4B in FIG. 2, the separation fromthe lower bed 1A being provided by the domed upper wall 3A of the lowerbed 1A. In this embodiment, the peripheral walls 2A and 2B and theskirts 6A and 6B of the embodiment of FIG. 2 are replaced by a singleshell 6. The tube 7, the opposite ends of which still communicate withthe opposite end zones of the adsorbers 1A and 1B, is closed offcentrally by a wall 14, the by-pass pipe 12 being, here, advantageouslyprovided directly between the nozzle pipes 11A and 11B. In thisembodiment, the other tubes 9'A and 9'B communicate respectively withthe upper and lower parts of the lower 1A and upper 1B adsorbers throughthe shell 6. The embodiment of FIG. 3 has greater compactness andincreased rigidity, the traversing tube 7 making it possible to take upthe compressive forces on the opposed walls 4A, 3B of the adsorbers andthus being suitable for applications employing high pressures.

Although the present invention has been described in relation toparticular embodiments, it is not limited thereby but, on the contrary,is capable of modifications and of variations which will be apparent tothe person skilled in the art.

We claim:
 1. A device for separating at least one component from a gasmixture, comprising at least a pair of adsorber units, each adsorberunit comprising an envelope defining an inner volume having a lower endzone and an upper end zone, at least one adsorbent layer between thelower and upper end zones, a first conduit means having one endcommunicating with the lower end zone, and a second conduit means havingone end communicating with the upper end zone, wherein the adsorberunits of the pairs are superposed and one of the first and secondconduit means of each adsorber includes a vertical central tube portion,the vertical central tube portions of the pair of adsorber units beingmechanically interconnected in endwise abutting relationship.
 2. Thedevice of claim 1, wherein the first and second conduit means eachinclude valve means.
 3. The device of claim 2, wherein the adsorberunits are superposed so as to define an intermediate space between themand wherein at least part of the valve means are disposed in theintermediate space.
 4. The device of claim 3, wherein the intermediatespace is at least part filled with an insulating material.
 5. The deviceof claim 1, wherein the vertical central tube portions are part of thesecond conduit means.
 6. The device of claim 1, wherein the verticalcentral tube portions of the absorber units of the pair are formed froma single tube.
 7. A gas separation device, comprising at least twoadsorber units each comprising an envelope defining an inner volumehaving a lower end zone and an upper end zone, at least one layer ofparticulate material between the lower and upper end zones, a firstconduit means including a vertical tube having one end opening into theupper end zone; a second conduit means having one end opening into thelower end zone, the adsorber units being superposed such that theenvelopes of adjacent units leave an intermediate space therebetween,the first and second conduit means each having an outer portionextending out of the envelope in the intermediate space.
 8. The deviceof claim 7, wherein the intermediate space is at least partly filledwith an insulating material.
 9. The device of claim 7, wherein the outerportion of the conduit means includes at least one valve.
 10. The deviceof claim 7, comprising a common supporting cylindrical casing.
 11. Thedevice of claim 10, comprising at least three superposed absorber units,the cylindrical casing forming a peripheral part of each envelope. 12.The device of claim 7, wherein said vertical tube extends through theassociated said layer of particulate material.